Auxiliary valve gear mechanism



Nov. 17, 1936.

A. O. J UDSON AUXILIARY VALVE GEAR MECHANISM Filed Dec. lO, 1934 5 Sheets-Sheet l @www Nov. 17, 1936. A. o. JUDSON AUXlLIARY VALVE GEAR MECHANISM Filed Deo. lO, 1954 3 Sheets-Sheet 2 nrw,

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Patented Nov. 17, 1936 UNITED STATES PATENT OFFICE Alfred 0. Judson, Swanton, Ohio, assignor to The Pilliod Company, Swanton, Ohio, a corporation of Ohio Application December 10, 1934, Serial No. '756,721

4 Claims.

This invention relates to reciprocable piston engines, but more particularly to steam or expansible fluid engines of the reversible type, and an object is to produce a new and improved .auxiliary valve gear mechanism for an invention of this type having the novel features of construction, arrangement and operation hereinafter described.

Further objects and advantages of the invention are hereinafter set forth, and for purposes of illustration, but not of limitation, an embodiment of the invention is shown in the accompanying drawings, in which:

Figure 1 is a side elevation partly in vertical section of a valve gear arrangement, valve chest and associated parts, showing the valve gear in neutral position while the piston is at midstroke;

Figure 2 is a top plan view of the auxiliary valve gear mechanism;

Figure is a vertical sectional elevation of the auxiliary valve gear mechanism taken substantially on the line 3-3 of Figure 4;

Figure 4 is a vertical sectional elevation taken substantially on the line 4-4 of Figure 3;

Figures 5, 6, '7` and 8 are diagrammatic views showing the position of the parts at the points of lead, cut-oli, release and compression, with the valve gear adjusted to 4approximately 25% forward motion cut-01T, and Figure 9 is a diagrammatic view similar to Figure 5 showing an inoperative structure having a straight combination lever.

The illustrated embodiment of the invention comprises a valve gear mechanism for imparting reciprocatory movements to the steam admission .and exhaust valve, the novel features being illustrated but the remaining parts being omitted, since such parts are well known tothose skilled in this art and detailed description and illustration .are not considered necessary to an intelligent understanding of this invention. It will be readily recognized by those skilled in this art that the arrangement herein shown and described may be used in conjunction with any well known. valve gear mechanism, a portion of the well known Baker gear being illustrated, viz., the bell crank IG which derives its oscillatory movement through a system of links and levers, eccentrio pin II on the driven wheel I2 of the engine or locomotive.

To the lower end of the vertical arm of the bell crank I3 is pivoted a valve rod I3, which inclines forwardly and upwardly, the forward end being pivotally mounted on a pin I4 carried by the bifurcated upper end I5 of a vertically disposed combination lever I6, the bifurcated upper end portion I5 of the combination lever providing arms I5@ an-d I5b and the outer end of the valve rod I3 being disposed between these arms. Pivotally connected to the lower end of the combination lever I6 is a union link I1, which is connectedV in the usual manner to the main crosshead I8 of the engine, which in turn is connected by the usual connecting rod I9 to the driven wheel I2 of the engine.

The combination lever I6 is suspended o-r supported from a valve stem crosshead guide 20 by a pair of radius bars 2 I disposed on opposite sides of the combination lever. 'Ihe upper ends of the radius bars 2l are bifurcated and arey pivotally connected to brackets 22 depending from the crosshead guide 20, and at their lower ends the radius bars are connected to a lower end portion of the combination lever by a pin 23. The pin 23 is disposed a relatively short distance upwardly from the lower end of the combination lever.

Reciprocable horizontally in the crosshead guide 2Ilis a valve stem crosshead 24', the forward end of which is connected by a stern 25 to a spool valve 26 of the usual type, which reciprocates in bushings 21 dispo-sed within a valve chest 23 having cylindrical ports 29 arranged in the usual manner at opposite ends of the chest Steam is admitted in the usual manner through a central steam admission passage 30 and ports 3I in the bushings 2l to enable admission of live steam to and exhaust of spent steam from the cylinder 32 through passages 33 at opposite ends of the cylinder. A piston 34 is reciprocable within the cylinder 32 and is connected to the main engine crosshead I8 by a piston rod 35.

The arms I5ad and I5a of the combination lever I6 are formed with rearward extensions 36, and mounted in the .rearwardY extensions 36 is a pin 3l to which are connected arms 38 of a yoke 39, the opposite end ofwhich is pivotally mounted on a pin All. secured to the valve stem crosshead 24. It will be noted that the arms 38 of the yoke 39' are disposed on the outer sides of the` arms I5.EL and I5b of the combination lever IB.

It. will be understood that the usual valve gear arrangement, of which the bell crank I0 forms a part, imparts the port opening travel to the valve 26 through the above described connections, and the operation of this gear is controlled in the usual manner from a remote point, such as the locomotive cab, for increasing or diminishing the percentage of the cut-ofi and the direction of movement of the locomotive or engine. Detail description of this mechanism and the operation thereof is not considered necessary here for a proper understanding of this invention. The lap and lead movements for the valves are obtained from the movements imparted to the combination lever I6 from the main crosshead I8. These mechanisms operate conjointly in such manner that movement of the valve 26 is accelerated at the desired points in its travel as well as retarded at the desired points in order to effect acceleration and dwell in the proper position. Retardation of the valve movement is desired as soon as a volume of steam is supplied to the main cylinder 32 suicient to drive the piston by its expansive properties in one direction so that the valve closes the respective port openings and fully opens the exhaust, thereby making most elicient use of the expansive properties of the steam.

The acceleration of movement and dwell in the travel of the valve 26 are due to the manner in which the combination lever |6 is constructed and connected to the valve stem 25 and valve rod |3. This auxiliary gear operates on the principle of a variable lap instead of a constant lap, as generally used heretofore, and that the distance between the pin 40 and pin |4 varies at different points in the piston stroke. On each dead center these parts are at their maximum distance apart, but at mid-stroke they are at their minimum distance apart. v'I'his variation in the relative positions of the pins 40 and I4 is caused by the swinging movement of the radius bars 2| which operate gradually to raise the combination lever |6 as they approach from midposition to each end of their stroke and gradually to lower the combination lever as they swing from their end or extreme positions to midposition.

Such variation in the relative position of the pins 40 and |4 causes the valve 26 to accelerate on each end of the valve stroke and to retard in the middle of the stroke, thereby producing larger steam and exhaust openings when the engine is operating at relatively short cut-ols. Retardation of the central portion of the valve travel operates to lengthen the expansion period between the events of cut-off and release, and also to cause the event of compression to come later in the stroke, since it enables the piston 34 to travel a greater distance before the valve 26 operates to cover or uncover the cylinder ports 3|.

It is to be understood that movement of the valve 26 is accelerated due to the swinging movement of the radius bars 2|, causing the combination lever to move upwardly or downwardly depending upon the direction of swinging movement, thereby decreasing the distance between the pins 46 and I4, which operates to decrease the effective movement of the combination lever I6 with respect to the valve and allow the valve gear proper through the valve rod I3 to accomplish the valve movement. Such acceleration takes place during movement of the valve 26 from lead position to full steam port opening before reaching the cut-oi position, and also during the movement of the valve from point of release to end of stroke. Movement of the valve 26 from cut-off position to release position or in the intermediate portion of its travel because the valve rod I3 and combination lever I6 are being moved in the same direction but the effective movement of the combination lever is decreased for the reasons above explained, inasmuch as the distance between the pins 40 and |4 are gradually decreased.

It will be readily understood by those skilled in this art that the port opening movements are imparted to the main valve 26 by the valve rod I3 and main gear mechanism deriving motion from the driven wheel I2. The lap and lead movements for the valve, however, are effected through the link and lever connections with the main engine crosshead 58 and supplement those movements imparted by the valve rod. The port opening movements may be varied according to the desired percentage of cut-off, but the lap and lead movements are non-adjustable or operate in substantially the same manner regardless of the percentage of cut-off imposed on the valve rod.

The operation of the above described mechanism will be apparent from an examination of Figures 5 to 8, which show the position of the parts at the points of lead, cut-off, release and compression. In Figure 5 the parts are at leading position, steam being admitted to the forward end portion of the cylinder to drive the piston 34 to the left, the port 3| at the rear end of the cylinder being open to exhaust. It will be understood that the valve 26 travels a short distance forwardly in the direction of the arrow as the piston 34 starts its movement in the opposite direction. In Figure 6 the cut-off position is shown in which the valve 26 has permitted the desired volume of steam to pass to the cylinder through the forward cylinder port 3| and has moved to close such port. The movement of the valve 26 from lead position to full steam port opening before reaching cut-off, is accelerated due to the swinging movement of the radius bars 2|, causing the combination lever |6 to move downwardly, thereby decreasing the distance between the pins I4 and 4i), which operate to decrease the effective movement of the combination lever with respect to the valve gear and allows the valve gear proper through the valve rod I3 to accomplish the valve movement. The movement of the Valve 26 from full steam port opening to the point of cut-off is retarded because the valve rod I3 and combination lever are moving in the same direction, but the effective movement of the combination lever is decreased, as above explained.

Continued movement of the valve 26 rearwardly in the direction of the arrow shown on the valve, takes place, but the movement from cutoff to release positions is retarded for the reasons above explained inasmuch as the distance between the pins I4 and 4U is still decreasing. The release position is shown on Figure '7, and is the point at which the forward cylinder port 3| begins to be uncovered by the valve 26 for releasing the steam from in front of the piston. Subsequent to release, the event of compression occurs, at which time a small volume of steam is trapped in advance of the piston to cushion it at the end of the stroke. It will be noted on Figure 8 that the rear cylinder port 3| is covered by the valve 26, and the piston 34 has approximately reached the end of its travel, steam remaining in the end of the cylinder being trapped and providing a cushion for the piston. The event of compression Should take place late in the piston stroke and the above described mechanism enables such compression to take place when merely suicient steam is retained to cushion the piston when the latter has approached close to the end of the stroke.

Due to the mounting of the combination lever and its connection to the valve stem 25 through the cross head and arms or links 38, the movement of the valve 26 from the point of release to that oi compression is accelerated since the pins I4 and 49 are being moved apart due to the raising of the combination lever I6 by the upward swinging movement of the radius bars 29. Movement of the valve 25 is retarded in the intermediate portion of its travel or between the points of cut-off and release to make most eiiicient use of the expansive properties of the steam, but at the opposite ends of the travel or at points of lead and compressi-on, the movement of the valve is accelerated to admit an eX- haust steam quickly to and from the cylinder through the port openings and to provide merely suicient compression to cushion the piston at the end of its stroke.

In order more clearly to point out the advantages of the above structure, attention is directed to Figure 9 which is similar to Figure 5, like reference numerals being used with the addition of exponent a, except in Figure 9 there is shown a straight combination IiifL without the backset or rearward extension 36. The straight combination leverv necessitates shortening of the link 38 and it will be seen from Figure 9 that the link 38a is considerably shorter than the link 38. The angle between the link 38@L and the upper end of the combination lever is approximately 57 whereas the similar angle shown in Figure 5 is approximately 25. Since the parts in Figure 9 are in the same position as those in Figure 5, detail description of the operation is unnecessary, it being suiiicient toV point out that the lower end of the combination lever is being moved by the union link I8a to the left of the iigure, the radius bars 2lau causing it to move downwardly while the upper end is moved forwardly by the valve rod Ia. As hereinbef-ore pointed out, the combination lever I6 of Figure 5 moves upwardly at this point instead of downwardly, because it is on the other side of the radius bars 2I. Due to the sharp angle of the relatively short link 38a, downward movement of the combination lever imposes such a cramping stress on the pin 40 as to bind the valve stem crosshead in its guide and if such downward and swinging movements continue the combination lever` will either bend or break.

It would be impracticable to shorten the valve stem 2521 and lengthen the link 38a, because shortening the valve stem would reduce the clearance and prevent a valve stroke of proper length. Even if this could be done, the result would be a decidedly different and noticeably inferior timing action.

Considering Figures to 8 inclusive, and noticing the movement of the combination lever with respect to the pivot point I4, it will be noted that it swings progressively to the left about that point from Figures 5 to 8. Since the point at which the link 38 is pivoted to the combination lever is to the left of the pivot point I4 in Figure 5, all of the pivotal movement about I4 tends to raise that connection, swinging the link into line with the valve stem 25 and retarding the stroke of the valve until the position of Figure 7 is reached. In this position the portion of the combination lever about the linlgtlis so nearly horizontal that its continuing movement about the pivot Ill is almost entirely a lifting movement, as has been pointed out. Obviously if the combination lever were straightened as indicated in Figure 9, the pivotal connection with the link 38 would be to the right of the pivot I4 when starting from the position shown in Figure 5 and, therefore, this pivotal connection would be lowered by the swinging movement about the point i4 which would produce the opposite effect from that desired. Even in the position corresponding to those of Figures 7 and 8 there would be comparatively little lifting action, the nal position of the pivotal connection between the link and combination lever being only about the same height as in Figure 5, so far as affected by swinging about the point I4. Therefore, the desired effect upon the timing of the valve could n-ot be obtained.

lt is to be understood that numerous changes in details of construction, arrangement and operation may be effected without departing from the spirit of the invention, especially as defined in the appended claims.

What I claim is new and desire to secure by Letters Patent is:

1. Valve gear mechanism for steam engines having a driven rotatable member, a driven reciprocable member, a steam admission and exhaust valve, said mechanism comprising a vertically disposed combination lever deriving motion at its lower end portion from said reciprocable member and at its upper end portion from said rotatable member, a reciprocable cross-head for said valve, a depending radius bar pivoted to a lower portion of said combination lever, means providing a pivotal mounting for the upper end of said radius bar, a rearwardly extending portion on the upper end of said combination lever, and link means providing a connection between said crosshead and said rearwardly extending portion of said combination lever.

2. Valve gear mechanism for steam engines having a driven rotatable member, a driven reciprocable member, a steam admission and exhaust valve, said mechanism comprising a vertically disposed combination lever deriving motion at its lower end portion from said reciprocable member and at its upper end portion from said rotatable member, a reciprocable cross-head for said valve, a depending radius bar pivoted to a lower portion of said combination lever, means providing a pivotal mounting for the upper end of said radius bar, the upper end of said combinatio-n lever being biiurcated, a rearward extension on the bifurcated portion of said combination lever disposed close to the Lipper end thereof, and a yoke pivoted at one end to said crosshead and extending outwardly therefrom intoI pivotal engagement with and in straddling relation to said rearward extension.

3. Valve gear mechanism` for steam engines having a driven rotatable member, a driven reciprocable member and a steam admission and exhaust valve, said mechanism comprising a vertically disposed combination lever deriving motion at its lower end portion from said reciprocable member and at its extreme upper end portion from said rotatable member, a reciprocable cross-head for said valve, a depending radius bar pivoted at its lower end to a lower portion of said combination lever, means providing a pivotal mounting for the upper end of said radius bar, and a link pivoted at -o-ne end to said crosshead, extending outwardly therefrom and pivoted at its opposite end to said combination lever a short distance below the upper end thereof.

4. Valve gear mechanism for steam engines having a driven rotatable member, a driven reciprocable member and a steam admission and exhaust valve, said mechanism comprising a combination lever deriving motion at its lower end portion from said reciprocable member and at its extreme upper end portion from said rotatable member, a reciprocabie cross head for said valve, a depending radius bar, a pivotal connection between a lower end portion of said combination lever and said radius bar, a rearward extension on the upper end portion of said combination lever, and link means connecting said cross head and said rearward extension.

ALFRED O. JUDSON. 

